Such an actuator unit for reciprocating piston internal combustion engines is known from WO 2010/097298 A1. The permanent magnets in active connection with the electromagnetic unit are attached to the inner ends of the control needles. Springs that apply a load on the control needles and also the permanent magnets in the direction of the clamping bodies and clamp these clamping bodies together for fixing the actuator pins in their inner position contact the control needles, while the electromagnetic unit draws the permanent magnets and thus the control needles against the force of the springs and thus releases the clamping bodies.
It has been shown that the actuator pins are not quickly locked in place due to the ejection ramp when pushed in or become unlocked in the latch device, e.g., due to vibrations of the reciprocating piston internal combustion engine, and contact the displacement grooves or the peripheral area adjacent to the displacement grooves in an undesired way. The undesired release of the latched state can also occur if the actuator pin travels over edges on the peak circle of the displacement cam unit. If the actuator pin slips in the direction of the cam contours of the sliding cam unit, then it will be set back when traveling over the ejection ramp, i.e., the lowered actuator pin is pushed back to the level of the peak circle of the sliding cam unit. In this case, the control needle should ensure the locking of the latch device again immediately after pushing the actuator pin up, which is only the case if the acceleration caused by the spring force of the control needle is high enough to create the locked state quickly enough, which is not, however, always the case.
In order to be able to eject the actuator pin quickly enough even at low temperatures and poor viscosity of the engine oil, the spring on the actuator pin must have a sufficiently strong construction. This has the result that the acceleration caused by the spring on the actuator pins, especially for warm reciprocating piston internal combustion engines, is high enough that an incorrect latching by the control needles is amplified.